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The aim of this paper is to review the developments in the use of superabsorbent polymer (SAP) in cementitious materials. This review covers the classification, properties, and methods for testing SAP, along with its impact on concrete properties, and other noteworthy developments in SAP usage. Various methods can be used to test the water absorption by SAP. Among them, the tea bag method is considered a simple and time-saving test, while centrifuge and suction filtration methods are regarded as accurate because they remove inter-particle liquid. The water absorption by SAP is affected by factors such as SAP composition, method of preparation, physical characteristics, and properties of the fluid. Higher fluid temperature (e.g., 60 °C) leads to greater absorption and release distance, while higher pH levels (pH 13) result in lesser absorption. The optimal dosage of SAP varies between studies, generally ranging from 0.1% to 1.5%. Higher SAP content (0.3–8%) reduces workability and decreases slump. Results related to strength vary; some studies have reported increased strength due to SAP's maintenance of higher internal relative humidity, while others have observed decreased strength due to increased porosity caused by SAP. The inclusion of SAP typically leads to a strength recovery of about 10% over time due to the continuous hydration process. Curing methods also influence strength, with sealed curing showing greater strength. Additionally, an increase in SAP dosage (0.1–0.6%) reduces shrinkage. Furthermore, the paper discusses the challenges encountered while using and testing SAP, as well as the explanations provided by researchers. [ABSTRACT FROM AUTHOR]

Monocarboaluminate is the major phase in calcium aluminate cements and is the main AFm phase in modern cement that incorporates limestone additions, including limestone calcined clay cement. This study reports thermal, elastic, and transport properties of monocarboaluminate obtained from molecular simulations. Properties and structural features are computed as a function of the relative humidity (RH) and water content. Full elastic, thermal expansion and thermal conductivity tensors are provided. Quantum‐corrected estimates are provided for the heat capacity and thermal conductivity. Self‐diffusion of interlayer species is also quantified, accounting for the subdiffusive regime. This work contributes to completing property data for critical phases in cement systems. [ABSTRACT FROM AUTHOR]

Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM‐EDS) is an indispensable and versatile technique that provides detailed 2D spatial insights into the microstructure of heterogenous cementitious systems. To foster clear and systematic understanding of SEM‐EDS analysis in advancing research on cementitious materials, the state‐of‐the‐art principles, analytical approaches, and applications of SEM‐EDS analysis in cementitious systems are reviewed. This review aims to assist researchers in selecting the most appropriate strategy for SEM‐EDS analysis to quantify phase assemblage, elucidate environmental interactions, and investigate microstructure evolution in cementitious systems. The fundamental concepts related to equipment, signal generation, acquisition of diverse EDS data are first presented. Subsequently, various analysis approaches, including point analysis, grid analysis, and mapping analysis are discussed. This review then emphasizes the practical significance and potential value of SEM‐EDS analysis in addressing phase quantification challenges pertaining to cementitious systems. It is posited that the SEM‐EDS analysis holds the promise of becoming the characterization backbone for quantitative research on cementitious systems. [ABSTRACT FROM AUTHOR]

This study explores the fabrication of cement-based sensors blended with supplementary cementitious materials (SCM) using carbonation curing. The effects of SCM types (i.e. fly ash or slag) and curing conditions on degree of carbon dioxide uptake, compressive strength, electrical conductivity and piezoresistive sensing capability were systematically examined. The results indicate that the inclusion of fly ash or slag enhances the degree of carbon dioxide uptake. However, it is also found that the excessive carbonation curing negatively affects compressive strength. Electrical resistivity is increased after carbonation curing due to carbonation-induced hydrate formation disrupting carbon nanotube-based conductive networks. The piezoresistive sensing capability is influenced by binder types and curing conditions, with higher sensitivity observed in samples blended with fly ash. [ABSTRACT FROM AUTHOR]

Recent decades have witnessed the increasing use of soil mixing technology to construct cut-off walls for groundwater control or underground pollutant containment. The strength and permeability of soil mix columns deteriorate considerably when subjected to chemical, mechanical and environmental stresses, leading to the need for repair of crack-originated damage. The development of self-healing grouts could provide more resilient and sustainable soil mix cut-off walls. In this study, for the first time, self-healing soil mix columns incorporating reactive magnesium oxide pellets were developed. The magnesium oxide-based cementitious grout was mixed with a sand soil using a laboratory-scale auger, and the embedded magnesium oxide pellets were ruptured upon cracking, producing expansive healing products due to hydration and carbonation, which can significantly fill the crack volume. The effects of magnesium oxide on the grout and soil mix samples were investigated in terms of both fresh and hardened properties. In addition, the self-healing performance was evaluated by examining permeability recovery and crack closure, and the microstructure and morphology of the magnesium oxide pellets and healing products were analysed. The results demonstrate the great potential of reactive magnesium oxide pellets as a self-healing agent for soil mix cut-off wall materials. [ABSTRACT FROM AUTHOR]

Heavy-weight concrete (HWC) is a widely adopted radiation shielding material in the nuclear industry. In this study, two kinds of high-density aggregate, namely, iron sand (IS) and steel slag coarse aggregate (SSCA), were adopted to fully replace river sand and natural coarse aggregate, respectively, producing ultra-heavy-weight concrete (UHWC) with a unit weight >3800 kg/m3, to ensure excellent radiation shielding performance. However, IS and SSCA seriously impaired the passing ability of UHWC as the cement paste could not hold the IS and SSCA as firmly as natural aggregates, owing to their high density. To overcome this, the rheology of UHWC should be optimised by partially replacing the cement with superfine silica fume (SSF) and using a suitable amount of superplasticiser (SP) to enhance the wet packing density (WPD). A total of 28 UHWC mixes with different replacement ratios of SSF and different SP dosages were tested for segregation width, flowability, L-box passing ability, unit weight and WPD. Results revealed that incorporating an appropriate quantity of SSF and SP improved the WPD of UHWC, resulting in improved segregation resistance, enhanced flowability, increased passing ability and a higher unit weight. Lastly, there is a positive correlation between flowability, passing ability and WPD. [ABSTRACT FROM AUTHOR]

This article primarily focuses on optimizing the composition of cementitious materials, such as fly ash, ground granulated blast furnace slag, nano-silica, silica fume, and superabsorbent polymers, to investigate their effectiveness in mitigating early residual expansion deformation in steam-cured concrete. Additionally, it evaluates the long-term performance of steam-cured concrete samples incorporating these cementitious materials. The article concluded that replacing 30% of the cement in the concrete mix with 20% fly ash and 10% slag, along with the additional inclusion of 0.2% super absorbent polymers, yields the best results in mitigating the above deformation and enhancing the performance of steam-cured concrete. The recommended mix proportion suggested in the article for 1 cubic meter of concrete includes 315 kg of cement, 90 kg of fly ash, 45 kg of slag, 0.9 kg of super absorbent polymer, 660 kg of sand, 1210 kg of limestone aggregate, 135 kg of water, and 4 kg of superplasticizer. This approach also prevents the reduction or insufficient development of the later-stage mechanical properties of steam-cured concrete and improves its pore structure. By focusing on optimizing the cementitious system of steam-cured concrete, this article provides theoretical and technical support for the preparation of high-performance prefabricated steam-cured concrete components. [ABSTRACT FROM AUTHOR]

Nanomaterials have garnered significant attention in recent years for their potential to enhance the mechanical properties of cementitious construction materials, particularly in high-strength concrete applications. This review aims to explore the effects of various types of nanomaterials on the mechanical properties of concrete materials. Current developments in the synthesis, characterization, and use of nanomaterials in the field of cementitious materials are thoroughly examined in this review. The incorporation of various nanomaterials such as nano-silica, nano-titania, carbon nanotubes, nano-clay, and nano-alumina can significantly enhance the mechanical properties of cementitious construction materials, particularly in high-strength concrete applications. These nanomaterials contribute to denser microstructures, improved hydration products, and enhanced interfacial bonding within the cement matrix, ultimately leading to superior mechanical performance. However, proper dispersion, dosage, and compatibility considerations are essential to realize the full potential of nanomaterials in cementitious materials. The optimum % of NS in cement was reported to be between 1 and 8%, whereas the optimum % of graphene oxide (GO) in cement was reported to be only between 0.05 and 0.5%, imparting high strength characteristics to concrete. The findings of the study promote the use of nanoparticles in cement concrete to enhance the strength of high-rise concrete buildings. The results of various studies are compared, and some significant recommendations are also made. Furthermore, this research underscores the practical applications of nanocomposite-based concrete materials while acknowledging their limitations and opportunities. [ABSTRACT FROM AUTHOR]

The activation product chlorine-36 (36Cl) is an important radionuclide within the context of the disposal of nuclear wastes, due to its long half-life and environmental mobility. Its behaviour in a range of potential cementitious encapsulants and backfill materials was studied by evaluating its uptake by pure cement hydration phases and hardened cement pastes (HCP). Limited uptake of chloride was observed on calcium silicate hydrates (C-S-H) by electrostatic sorption and by calcium monosulphoferroaluminate hydrate (AFm) phases, due to anion exchange/solid solution formation. Diffusion of 36Cl through cured monolithic HCP samples, representative of cementitious materials considered for use in deep geological repositories across Europe, revealed a markedly diverse migration behaviour. Two of the matrices, a ground granulated blast furnace slag/ordinary Portland cement blend (GGBS–OPC) and an ordinary Portland cement (CEM I) effectively retarded 36Cl migration, retaining the radionuclide in narrow, reactive zones. The migration behaviour of 36Cl within the cementitious matrices is not strictly correlated to the measured sorption distribution ratios (Rd-values), suggesting that physical factors related to the microstructure can also have a distinct effect on diffusion behaviour. The findings have implications when selecting cementitious grouts and/or backfill materials for 36Cl-bearing radioactive wastes. [ABSTRACT FROM AUTHOR]

AbstractCementitious materials are susceptible to cracking and spalling during service by various internal and external factors, while the long setting time and limited initial strength of Portland cement are insufficient for the repair project’s requirements. Cement can be categorized into Portland cement, sulphoaluminate cement, ferroaluminate cement, aluminate cement, phosphate cement, and fluoroaluminate cement based on various water-hardening ingredients. This paper summarized the performance of various cements and discussed the advancements in studying the impact of nanomaterials and major mineral admixtures (fly ash, silica fume, mineral powder, and slag) on the physical properties and mechanical properties of Portland cementitious materials and special cementitious materials. These additives can expedite the setting process, enhance flowability, and boost the strength of cementitious materials. This paper discussed the impact of nanomaterials and mineral admixtures on the hydration mechanisms of various cementitious materials. Mineral admixtures and nanomaterials can regulate the cementitious material hydration process and improve pore structure. On this basis, the problems to be studied in depth in the application of different kinds of cement in repair works were proposed. [ABSTRACT FROM AUTHOR]

Cement-based construction materials, commonly known as "cement concrete", result from the hydration reaction of cement, which releases heat. Numerous studies have examined the heat of cement hydration and other thermal properties of these materials. However, a significant gap in the literature is the assessment of the impact of the hydration temperature on the material's strength, particularly compressive strength. This work presents an experimental methodology that consistently estimates the temperature evolution of a mixture used to manufacture concrete or mortar during the first hours of Portland cement hydration. The methodology aims to ensure results that correspond to an infinite medium (adiabatic conditions), where there are no heat losses to the surroundings. Results obtained under adiabatic conditions (simulating an infinite medium) indicate that a ready-made mortar (Portland cement: sand: water; 1:2.5:0.5) can reach temperatures of approximately 100 °C after 48 h of hydration. Under these conditions, compressive strength decreases by up to 20%. [ABSTRACT FROM AUTHOR]

In this paper, an extension of the Timoshenko model for plane beams is outlined, with the aim of describing, under the assumption of small displacements and strains, a class of dissipative mechanisms observed in cementitious materials. In the spirit of micromorphic continua, the modified beam model includes a novel kinematic descriptor, conceived as an average sliding relevant to a density of micro-cracks not varying along time. For the pairs of rough surfaces, in which such a distribution of micro-cracks is articulated, both an elastic deformation and a frictional dissipation are considered, similarly to what occurs for the fingers of the joints having a tooth saw profile. The system of governing differential equations, of the second order, is provided by a variational approach, endowed by standard boundary conditions. To this purpose, a generalized version of the principle of virtual work is used, in the spirit of Hamilton–Rayleigh approach, including as contributions: (i) the variation of the inner elastic energy, generated by the linear elasticity of the sound material and, in a nonlinear way, by the mutual, reversible deformation of the asperities inside the micro-cracks; (ii) the virtual work of the external actions consistent with the beam model, i.e., the distributed transversal forces and the moments per unit lengths; besides these two contributions, constituting the conservative part of the system, (iii) the dissipation due to friction specified through a smooth Rayleigh potential, entering a nonlinear dependence of viscous and Coulomb type on the sliding rate. Through a COMSOL Multiphysics implementation, 1D finite element analyses are carried out to simulate structural elements subjected to three- and four-point bending tests with alternating loading cycles. The dissipation of energy is investigated at varying the model parameters, and the predictions turn out to be in agreement with preliminary data from an experimental campaign. The present approach is expected to provide a valuable tool for the quantitative and comparative assessment of the hysteresis cycles, favoring the robust design of cementitious materials. [ABSTRACT FROM AUTHOR]

The construction industry has been increasingly concerned with the environment and sustainability, and one solution is engineered cementitious composites (ECC), which have self-healing, ductility, and strength properties. Researchers have been working to make ECC greener by creating synergistic mechanical interactions between fibers, matrices, and fiber–matrix interfaces. This study developed ECC using local river sand, silica fume, moderate to high-volume fly ash (FA), and bulky PVA fibers, evaluating workability and compressive strength at various testing ages (1, 7, 28, 60, and 180 days). According to the test findings, fresh ECC mortar mixtures exhibit an increase in workability with increasing FA content due to the spherical and glossy form of FA particles. All ECC samples have a compressive strength of over 20 MPa after 1 day, making them high-early compressive strength composites. The sample with the highest compressive strength after 28 days was 111.28 MPa. PVA fibers, FA, and SF contribute to increasing strength while using local river sand as an ingredient in composite mixtures is also beneficial. The samples experienced a bulging process during failure due to the use of oiled PVA fibers. The maximum load before the collapse was attained after a longer period of time where smeared cracks were visible on the samples' surface. Based on the analysis of the compressive strength over a period of more than 28 days, it is clear that both ECC mortar and bulky PVA-ECC samples exhibit sufficient strength stability. It is worth mentioning that as the curing age of ECC increases, there is a gradual increase in strength, although the level of increase is relatively slow. [ABSTRACT FROM AUTHOR]

Currently, all the cement consumed in the Northwest Territories (NWT), Canada, is imported from other provinces (e.g. Alberta) by long-distance (∼1800 km) freight truck. Transporting cement over long distances not only raises its cost, but also results in a higher carbon footprint. Producing cement locally is therefore a potential low carbon and economic solution for the local industry. However, it is unknown if the local raw materials are suitable for cement manufacture, and there is a lack of a critical raw material – iron ore – for cement manufacturing. However, instead of iron ore, there are iron-rich tailings from a local rare earth element (REE) mine. Towards a low carbon and circular economy, the use of local raw materials (i.e. limestone, clay and gypsum) and mine waste (REE tailings) to manufacture cement in the NWT was explored and the first bag of cement in the history of the NWT was produced. Concrete samples made with the NWT cement achieved strength comparable to that of concrete based on commercial ordinary Portland cement. In addition, it was estimated that locally producing cement in the NWT has the potential to reduce carbon dioxide emissions by 3.0–61.7% as compared with importing cement from other provinces. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Minerals & Processing / Huagong Kuangwu yu Jiagong is the property of Industrial Minerals & Processing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The use of biochar as a concrete constituent has been proposed to reduce the massive carbon footprint of concrete. Due to the low density and complex porosity of biochar, microstructural analysis of Portland cement-biochar composites is challenging. This causes challenges to the improvement of the micro-scale understanding of biochar composite behavior. This work advances the microstructural understanding of Portland cement composites with 0, 5, and 25 volume percent (vol%) of cement replaced with wood biochar by applying common characterization techniques of mercury intrusion porosimetry (MIP), gas sorption, scanning electron microscopy, and isothermal heat flow calorimetry (HFC) in conjunction with 1H nuclear magnetic resonance (NMR) and micro-X-ray computed tomography (XCT) analysis techniques. The combination of these techniques allows a multi-scale investigation of the effect of biochar on the microstructure of cement paste. NMR and XCT techniques allow the observation and quantification of the pore space. HFC and MIP confirmed that biochar absorbs moisture and reduces the effective water-cement ratio. Gas sorption, MIP, and NMR shows that 5 vol% replacement does not significantly affect the gel and capillary pore structures. Results from XCT (supported by MIP and NMR) show that biochar can reduce the formation of larger pores. Importantly, XCT results suggest that biochar can act as a flaw in the microstructure which could explain reductions in the mechanical properties. Overall, the mechanical properties already analyzed in the literature are consistent with the microstructural changes observed, and these results highlight the need to carefully tailor the volume fraction of biochar to control its effect on the paste microstructure. [ABSTRACT FROM AUTHOR]

Ground Granulated Blast Furnace Slag (GGBS) is an effective supplementary cementitious material because of its pozzolanic properties and positive environmental impact. This research explores the flexural strength of concrete pavements by analyzing several high-volume formulations of GGBS concrete against conventional mixes. The study aims to assess the viability of incorporating high-volume GGBS mixes in pavement construction, with a particular emphasis on their flexural performance. The study employs various GGBS content levels (60%, 65%, 70%, and 75%) in concrete mixes, with the control mix containing ordinary Portland cement. Specimens are prepared according to standard procedures, and flexural testing is conducted to evaluate their performance. Statistical analysis is performed to compare the flexural strength and behavior of GGBS mixes with the control mix. The results obtained from the experiments revealed that the GGBS concrete mixes had better flexural performance than the control mix, with more strength and less cost. The results provide the performance of large-volume GGBS concrete mixes under flexural loading circumstances, which helps to understand whether these mixes are suitable for use in concrete pavements. Ultimately, this research sheds light on the possibilities of utilizing large- volume GGBS concrete mixes as long-term substitutes for traditional concrete pavements, which may help in the promotion of greener and more long-lasting infrastructure solutions. [ABSTRACT FROM AUTHOR]

Copyright of GeSec: Revista de Gestao e Secretariado is the property of Sindicato das Secretarias e Secretarios do Estado de Sao Paulo (SINSESP) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of GeSec: Revista de Gestao e Secretariado is the property of Sindicato das Secretarias e Secretarios do Estado de Sao Paulo (SINSESP) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of GeSec: Revista de Gestao e Secretariado is the property of Sindicato das Secretarias e Secretarios do Estado de Sao Paulo (SINSESP) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Three-dimensional printing of cementitious materials for construction has been extensively investigated in recent years, with several demonstration projects successfully carried out. These efforts aim to leverage the printing process to achieve more efficient production of components compared to conventional concrete technologies. This includes both the process itself (eliminating the formwork stage) and the flexibility in producing complexly shaped elements. To maximize the potential of 3D printing in the construction industry, additional steps must be taken, grounded in a holistic view of the entire process. This involves integration of the production chain, including design, materials, and manufacturing of components, to create elements with optimal performance, encompassing structural, environmental, and architectural aspects. Such multi-functionality requires the viewing of 3D printing not just as a production technology but as a platform enabling the integration of all these components. To advance this approach, quantitative tools are developed to optimize the following three key components: material composition; manufacturing parameters to ensure buildability; and design tools to optimize multiple performance criteria, particularly structural and architectural shape. A demonstration component, namely a post-tensioned beam, featuring two multi-functional characteristics—structural and architectural—is designed, produced, and evaluated. The scientific concepts and research tools used to develop these quantitative design tools are multidisciplinary, including rheological characterization, control of the internal structure and composition of granular materials, simulation of the mechanical behavior of green material during printing, and the hardened properties of the components, all utilizing structural optimization to enhance performance. [ABSTRACT FROM AUTHOR]

The effect of graphene oxide(GO) on the mechanical properties and microstructure of cement-based materials is studied through mechanical property test and microscopic test methods such as scanning electron microscope(SEM), X-ray diffraction(XRD). Testing results show that compared with the blank sample, the addition of 0. 02% GO improves the early compressive and flexural strengths of cement paste specimens obviously. Meanwhile, the addition of GO transforms the aggregation state of Ca(OH)2 crystal, refines the size of CH crystal and makes the structure of cement paste more compact. In order to explore the influence mechanism of GO on cement hydration reaction from the atomic / molecular level, molecular dynamics simulation software Materials Studio (MS) is used to simulate the movement and aggregation of cement hydration products(CH) on the surface of GO. The simulation results show that with the progress of hydration reaction, calcium ions and hydroxyl ions move towards the sites of hydrophilic oxygen-containing group, gradually gather around GO molecules and facilitates the formation of CH crystals. With the addition of GO, the Young's modulus of CH microstructure model increased by 26. 9% compared to the model without GO, indicating that GO can effectively improve the mechanical properties of CH hydration products. The simulation results are in good agreement with the mechanical and micro performance test results, which can provide a theoretical reference for the design and application of molecular dynamics simulation technology in GO cement-based materials. [ABSTRACT FROM AUTHOR]

Raman spectroscopy (RS) has attracted significant attention for the analysis of cementitious materials owing to its remarkable spatial and spectral resolution, which enable the precise investigation of chemical bonds, mineral phases, and microstructures. This review focuses on applications of RS for characterizing cement clinker compositions, monitoring hydration processes, and detecting durability issues, with a particular focus on advancements in quantitative analysis and imaging techniques in recent years. The featured Raman vibration bands are summarized, which are useful for the identification of calcium silicate‐related substances. The current technical limitations of RS for investigating cementitious materials are discussed, and potential approaches to overcome these limitations are proposed. The technological innovations in RS will further enhance its efficacy and applicability for investigations of cementitious materials, thus facilitating a comprehensive understanding of the life cycle of cement across various scales of interest. [ABSTRACT FROM AUTHOR]

In this study, the use of meta-schist as an alternative to sand–clay in preparing cement raw mixtures was investigated for the first time. To produce the highest quality Portland cement clinker by examining the mineral and chemical properties of meta-schists, two different raw meal samples were prepared, utilising conventional cement clay as a baseline sample ((PC)Ref) and the other with meta-schist ((PC)MSC). The effects of both raw mixtures on burnability tests and reactivity were evaluated based on the unreacted lime content in samples after they had been sintered at 1200, 1300, 1350, 1400 and 1450°C. The porosity amount, distribution, grain structure of silicate phase crystals, and equivalent crystal diameters and amounts of meta-schist clinker phases (C3S, C2S, C3A and C4AF) examined by polarising optical microscope showed that they are suitable for the production of PC. The hydration products of the cement mortars were determined by scanning electron microscopy and energy-dispersive X-ray analysis at 2, 7 and 28 days. In addition, the compressive strength test results of (PC)MSC and (PC)Ref mortars after 28 days of curing ranged between 57 and 55.5 MPa, and the cement produced was classified as CEM I 42.5R. [ABSTRACT FROM AUTHOR]

The low activity of stainless steel slag (SSS), primarily attributed to its high γ-C2S and low C3S content, impedes its effective utilisation. A thermochemical high-temperature reconstruction method using lime and bauxite as tempering agents to regulate the mineral phase was investigated in this work. Through an array of tests and analytical techniques, including compressive strength tests, activity index evaluation, X-ray diffraction, scanning electron microscopy and hydration heat analysis, the impacts of the calcium/silicon mass (CSM) ratio and the sintering temperature on the mechanical properties and activity of reconstituted SSS mortar were examined. It was found that, at a CSM ratio of 4.2 and a sintering temperature of 1290°C, the reconstructed slag demonstrated optimal mechanical properties and activity, yielding compressive strengths of 43.69 MPa and 62.58 MPa at 7 days and 28 days, respectively, with remarkable 28-day activity index of 143.49%. The proposed thermochemical high-temperature reconstruction method ingeniously employs high temperature to increase the content of C3S while rapid cooling prevents alteration of the C2S crystalline structure. This innovation significantly enhanced the mechanical properties and activity of the SSS, offering promising avenues to increase its utilisation rate. [ABSTRACT FROM AUTHOR]

Several researches conducted on rubberized concrete in the past but very few researchers explained the bonding effect of the waste tire rubber particles with different cementitious materials. In this research the effect of the fineness of the micro silica and its bonding with the rubber particles is studied. To check the influence of fractional replacement of cement using micro silica and discarded tire rubber as limited substitution of sand with providing pre-treatment to rubber particles, this experimental investigation has been conducted on concrete with varying percentage switch of cement using micro silica (SF), especially micro-silica was used in this study to exchange with cement by its weight. SF exchanged cement from 0% to 12% with an incremental ratio of 3%. Along with this, the sand was fractionally replaced using pretreated crumb rubber (CR) particles derived from end-of-life tires. The replacement ratio changed by 5% by the volume of sand, ranging from 0% to 20%. The pre-treatment process for CR was done using Sodium Hydroxide (NaOH) of 1 Molarity, for achieving good bonding between cementitious material paste and rubber particles. Distinct fresh and hydrated concrete properties were assessed and compared with normal concrete (NC) having 0% SF and 0% CR. 17 concrete mixtures in all, together with the control mix, were assessed in this study with varying amounts of SF and CR. The bonding structure and impermeability were enhanced by using SF in concrete with promising enhancement in mechanical strengths. Based on the outcomes obtained from this research, the optimal proportion for partial substitution of cement and sand by SF and CR was fixed for the desired grade of concrete to provide an innovative form of concrete to the construction industry.

With the rapid development of the construction industry and higher requirements on the properties of materials, extensive studies have been made to improve the property of the concrete and cementitious materials. This paper mainly studies the mechanical property, anti-chlorine ion diffusion, anti-chlorine ion diffusion, anti-freezing performance, hydration process, microstructure and rheological property of the concrete and cementitious materials after adding cellulose nanofibers. Results showed that the compressive strength of C40 concrete with 0.15% cellulose nanofibers added was 75.72 MPa at 56 days of age, 23.11% higher than that of the control group. It was also higher than that of concrete with 0.20% cellulose nanofibers admixture added. When the content of cellulose nanofibers was 0.15%, the flexural strength reached the maximum value of 6.55 MPa, improving by 24% compared with the control group. Under the circumstances of 150 freeze-thaw cycles, the mass loss rate of C50 concrete with 0.15% CNFs admixture registered at 0.41%, reducing by 0.81% compared with the control group. However, when the cellulose nanofibers increased to 0.20%, the mass loss rate of the concrete reached 0.48%, indicating that adding an appropriate amount of cellulose nanofibers could improve the performance of the concrete. The study provides a strong scientific basis for modifying concrete and cementitious materials.

The use of non ferrous smelting slag to prepare new types of cementitious materials is an important way to realize the resource utilization of solid waste. The gelation mechanism and mechanical properties are the focus of research on non ferrous smelting slag based cementitious materials, and the leaning and solidification mechanisms of heavy metal ions have been receiving increasing attention nowadays. In this article, the morphology and structure of non ferrous smelting slag are described, the existence form and immobilization principle of heavy metal ions in non ferrous smelting slag based cementitious materials are summarized systematically. This review can provide reference for the study of heavy metal immobilization in the application of smelting slag based cementitious materials. [ABSTRACT FROM AUTHOR]

One of the most important hydration phases of Portland cement is ettringite, a calcium sulfo-aluminate mineral ( C a 6 A l 2 (O H) 12 (SO 4) 3 · 26 H 2 O ) showing a great capacity of adsorbing radionuclides and other contaminant cationic and anionic species, or incorporating them into its crystal structure. In this work, the X-ray diffraction pattern and infrared spectra of a synthetized ettringite sample are recorded and simulated, employing theoretical methods based on Density Functional Theory. Despite the complexity of this phase, the calculated structure, X-ray diffraction pattern and infrared spectrum are in excellent agreement with their experimental counterparts. Since the calculated and experimental spectra are consistent, the main infrared bands are assigned using a normal coordinate analysis, some of them being completely reassigned with respect to other experimental works. The good agreement found provides strong support for the computational methods employed towards their use for studying the surface adsorption properties and the incorporation of contaminations in its structure. The density of reactive groups at the surfaces of ettringite is reported, and the surface adsorption of water molecules is studied. These surfaces appear to be highly hydrophilic, in agreement with the experimental finding that the ettringite structure may include more water molecules, at least up to 27, one more than in its standard formula. [ABSTRACT FROM AUTHOR]

Supplementary cementitious materials (SCMs) are commonly introduced into the concrete mix to increase their properties, addressing the current need for durable and robust pavements. With every ton of Ordinary Portland Cement (OPC) produced through processes such as fossil fuel combustion and limestone fermentation, carbon dioxide is released into the atmosphere. Conversely, Ground Granulated Blast-furnace Slag (GGBS), being abundantly available, presents a viable more environmentally friendly alternative to cement for various concrete applications. This work studies the influence of GGBS, in combination with chemical admixtures, on M40 grade binary blended concrete mixtures. The aim of the study was to improve the strength characteristics at various stages of concrete curing. The results indicated that the GGBS-incorporated concretes (replacing 60%, 65%, and 70% of the cement) exhibited an increase in compressive strength after prolonged curing. The average density of fresh concrete mixes containing GGBS did not exhibited a noticeable increase. A marginal disparity in air content was observed in the replacement mix. Minimal length changes were observed in the drying shrinkage test after a curing duration of 360 days compared to conventional concrete mixtures. [ABSTRACT FROM AUTHOR]

In this study, comprehensive investigation of the shrinkage compensation mechanisms of calcium-based expansive agents (CEAs), their effects on the properties of (ultra) high-strength concrete (HSC/UHSC), and the existing problems in applying this methodology was conducted. Analyses showed that the rational use of CEAs under certain conditions could greatly or completely inhibit the development of autogenous shrinkage of HSC/UHSC and significantly reduce the risk of associated cracking. However, it was found that the hydration of the CEAs affected the hydration process of other binders, thereby altering the microstructure of concrete. This, in turn, led to a reduction in mechanical properties such as compressive strength, flexural strength, and elastic modulus, with the rate of reduction increasing as the amount of CEA used increased. Moreover, when attempting to improve the shrinkage compensation effects, increasing the amount of CEA presented a risk of delayed expansion cracking of the HSC/UHSC. Neither the expansion mechanism, expansion conditions, nor the inhibition methods have yet been fully clarified in the current stage. Lastly, newly proposed Ca–Mg composite EAs were outlined, and the research prospects of Ca–Mg composite EAs in HSC/UHSC were explored. [ABSTRACT FROM AUTHOR]

The use of industrial solid waste to capture and fix CO2 is a promising technology for CO2 sequestration. A thermogravimetric analyzer and CO2 cement hydration mixing device were used to study the effects of mixing method, curing system, temperature, CO2 concentration and other factors on the carbon fixation amount and performance of the circulating fluidized bed fly ash cement-based material system. The results showed that the carbon fixation and early strength of the cementitious materials could be improved by adding CO2 in the stirring process and making CO2 directly participate in the process reaction. The cementing materials samples prepared with CO2 were cured in a standard curing box for 2 days and a carbon atmosphere for 1 day, the carbon fixation amount of the cementing material was increased by 33% and the compressive strength of the cementing material was also improved. This is because under the combined action of carbon mixing and carbon curing, the prepared binding materials produced more Ca(OH)2 in the early stage, and it reacts with the introduced CO2 to form CaCO3. The strength of the calcium carbonate crystals is higher than the strength of the earlier stage of cement, and at the same time, the samples would solidify more CO2. Considering the carbon fixation amount, sample performance and solid waste utilization rate, the best conditions for the cementing materials are as follows: the content of the circulating fluidized bed fly ash (CFA) was 35%, the concentration of carbon curing was 30%, the curing temperature was 40 ℃, the water-binder ratio was 0.4, and the carbon fixation amount of the cementing material could reach about 20%. The use of CFBFA to solidify and storge CO2 is not only a new way to utilize high value-added fly ash resources, but also beneficial for reducing industrial carbon dioxide emissions. [ABSTRACT FROM AUTHOR]

An alkali-free liquid accelerator was prepared with aluminium sulfate and aluminium formate as the main components. The effects of the accelerator on the setting of paste and the mechanical strength of mortar were studied, and the impact of the accelerator on the early hydration behaviour and hydration products of the paste were investigated by isothermal calorimeter analysis, X-ray diffraction analysis, scanning electron microscopy and thermogravimetric analysis. The results show that the accelerator is excellent for the rapid setting and hardening of the cement. When the content of the accelerator was 8 wt%, the initial setting time and final setting time of the paste were 85 s and 180 s, respectively, and the strengths of the mortar at 1 day and 28 days were 9.52 MPa and 44.42 MPa, respectively. The proposed accelerator can accelerate the dissolution and hydration of tricalcium aluminate and tricalcium silicate and promote the formation of ettringite, formate and portlandite. [ABSTRACT FROM AUTHOR]

The scarcity of comprehensive data on the shear properties of reinforced GP‐concrete beams without shear reinforcement has hindered their widespread use, mainly due to challenges in predicting their shear performance. This study examines the influence of incorporating up to 15% waste glass powder (GP) with two separate particle size categories: GP‐A (55 to 135 μm) and GP‐B (finer than 55 μm) as a cement replacement on the 180‐day shear performance of reinforced concrete beams with varying cement content and without stirrups. To accomplish this, a total of 14 beams were used, all sharing identical dimensions measuring 200 mm × 250 mm × 2000 mm. The aforementioned parameters were investigated for their effects on the shear performance of beams, including crack patterns, modes of failure, load–deflection behavior, and strength capacities at different loading stages. Furthermore, this investigation explores the applicability of the most commonly used design codes of practice for predicting the shear strength of reinforced GP‐modified concrete beams. These codes are typically employed to design the shear strength of reinforced conventional concrete shallow beams without shear reinforcement. The study's findings indicate that the impact of GP particle size on the shear performance of beams with the same GP content is almost negligible. Additionally, the study found that incorporating GP into concrete beams does not have any negative effects on their cracking load capacity, shear strength, or flexural cracking load capacity. In fact, it can even improve the latter. A comparison of experimental results with predictions from the design codes revealed that both the CEB‐FIP (1990) equation and the ACI equations provided safe estimates of shear strength for the tested beams. However, the CEB‐FIP (1990) equation yielded predictions with a lower mean, standard deviation, and coefficient of variation compared with the ACI equations, suggesting a higher level of accuracy in its estimates. The findings affirm the suitability of GP‐concrete as a viable alternative in concrete structures specifically engineered to withstand shear forces. [ABSTRACT FROM AUTHOR]

To evaluate the effect of Microbial Induced Calcium Carbonate Precipitation (MICP) on the enhancement of early resistance to sulfate attack of cementitious materials. In this paper, firstly, the effect of Bacillus subtilis (BM) on the carbonation depth as well as the carbonation rate of standard as well as carbonation-conditioned cementitious sand specimens was investigated. Secondly, the compressive strength and volumetric deformation of the specimens at different ages of immersion in sulfate solution were investigated. Finally, the changes of hydration products before and after the addition of BM were analyzed by X-ray diffraction analysis (XRD), and the microscopic pore structure of the specimens after erosion was analyzed by low-field nuclear magnetic resonance (LF-NMR) and scanning electron microscope (SEM), which revealed the mechanism of the improvement of BM on the resistance to sulfate erosion of the cementitious materials. The results showed that the initial compressive strength of BM carbonised curing specimens, ordinary carbonised curing specimens and BM standard curing specimens were increased by 42.0%, 34.0% and 4.0%, respectively, compared with the ordinary standard curing specimens, respectively, compared with the control group, and the loss of the final compressive strength was reduced by 37.4%, 25.4%, and 14.5%, and the expansion rate was reduced by 31.3%, 22.0%, after sulfate erosion for 6 months, 5.2%, and porosity decreased by 24.2%, 13.6%, and 9.9%. Microbial mineralization accelerated the reaction between Ca2+ in the pore solution and atmospheric CO2, and the calcite formed filled the pores to make the structure denser, increasing the initial compressive strength of the specimens and reducing the loss of properties when exposed to sulfate solution. Therefore, the application of MICP technology in cementitious materials provides a new direction for the development of durable and sustainable cementitious materials. [ABSTRACT FROM AUTHOR]

Cement-based cementitious materials occupy a central position in the construction industry, but the problem of high carbon dioxide(CO2) emissions from cement production has attracted global attention. To meet this challenge, finding low-carbon alternative materials has become a top priority in the research of new building materials. At the same time, the problem of large amounts of lithium slag piling up needs to be solved, and resource utilization has become its potential way out. In this study, the volcanic ash activity of lithium slag was activated by composite activation means of high-temperature calcination and sodium silicate, and it was used as an alternative mix to cement. The Box–Behnken design and response surface method (BBD-RSM) was utilized to optimize the ratio of activated lithium slag composite cement-based cementitious materials, and high-performance new solid waste cementitious materials were prepared. The results show that activated lithium slag composite cementitious materials activated lithium slag exhibit excellent performance when activated lithium slag mass fraction is 7.3%, the sodium silicate dosage is 8.8%, and water–solid ratio is 0.6:1. The composite cementitious material under this ratio shows excellent performance, with fluidity 235.69 mm, gelation time 73.54 s, water evolution rate 1.123%, 3d and 28d compressive strengths, respectively, are 11.54 MPa and 22.9 MPa. Compared with ordinary Portland-cement-based cementing materials, the uniaxial compressive strength, modulus of elasticity, and tensile strength at break of activated lithium slag cementitious material solidified body were increased by 34.33%, 36.43%, and 34.98%, and the compressive deformation and tensile deformation were enhanced by 37.78% and 40%. This study not only provides a theoretical basis and experimental foundation for the preparation of new solid waste cementitious materials, but also provides a new solution for the reinforcement of crushed rock bodies in engineering practice, which is of great significance for promoting the low-carbon development of the construction industry. [ABSTRACT FROM AUTHOR]

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Soft to medium clay soil possesses major sources of damages to the pavement layers overlying them because of their potential failure under moisture changes and external heavy traffic load. In such situations, soil stabilization methods can be used to improve the soil properties and satisfy the desired engineering requirements. This study presents the use of sugarcane bagasse ash (SBA) and lime as chemical stabilizers for a clay soil subbase. Sugarcane bagasse ash and lime are used individually and as mixtures at varying percentages to stabilize a clay soil from Taxila, Pakistan. Various geotechnical laboratory tests such as Atterberg limits, compaction test, and California Bearing Ratio (CBR) are carried out on both pure and stabilized soils. These tests are performed at 2.5%, 5%, and 7.5% of either SBA or lime by weight of dry soil. In addition, mixtures of lime and SBA in ratios of 1:1, 2:1, 3:1, 1:2, and 1:3 are used in 5%, 7.5%, and 10% of dry soil weight, respectively. Results indicate that soil improved with 7.5% SBA showed a 28% increase in the liquid limit, while soil mixed with 2.5% lime in combination with 7.5% SBA showed an increase of 40% in the plastic limit. For the plasticity index, the soil mixed with 7.5% SBA showed an increase of 42%. Moreover, 2.5% lime in combination with 2.5% SBA showed the best improvement in soil consistency as this mixture reduced the soil plasticity from high to low according to the plasticity chart. Furthermore, 2.5% SBA in combination with 5% lime demonstrated the largest improvement on the CBR value, which is about a 69% increase above that of the pure soil. Finally, the cost analysis indicates a promising improvement method that reduces pavement cost, increases design life, and mitigates issues of energy consumption and pollution related to SBA as a solid waste material. [ABSTRACT FROM AUTHOR]

Nanomaterials are incorporated to improve the characteristics of conventional concrete materials. Among them, Titanium dioxide (TiO2) nanoparticles exhibit sustainable concrete features such as optimization of materials, improvement of structures, recycling, and innovative waste management in materials and processes. This paper thoroughly elaborates on the effect of TiO2 nanoparticles on the composites of cement which in turn modifies the physical, mechanical, and ability to resist any chemical action, climate change, and abrasion; Furthermore, this study emphasizes the small fragment size, increased surface area and photocatalytic properties of cementitious composites. The key parameters for choosing TiO2 nanoparticles encompass their strength, antimicrobial characteristics, and stability against external environmental factors, covering a wide range of compatibility issues and exploring the fundamental characteristics of the material imbibing in cement. The present review includes the basic features of TiO2 nanoparticles, their utilization in cement, the fabrication processes, and influential factors on the workability of concrete. The review also comprises the workability of fresh concrete, mechanical qualities related to compressive, flexural, and tensile strength, and durability variables such as electrical resistivity, permeability, carbonation resistance, freeze-thaw cycles, and sulfate attack resistance. The report further investigates the ideal dosage of TiO2 nanoparticles and compares it to other nanomaterials utilized in cementitious compositions. More importantly, it emphasizes nano-titanium dioxide's ability to deal with pollutants in urban areas, notably nitrogen oxides (NOx), via its photocatalytic characteristics. The study explains how nano-TiO2 affects the microstructure of cement-based materials, resulting in improved durability, performance, and mechanical characteristics. Finally, this study outlines present problems and recommends future research using nano-TiO2 in cement-based materials.

In recent years, a discernible surge in greenhouse gas emissions has precipitated severe global warming, with the construction industry identified as a notable contributor, particularly through carbon dioxide emissions from cement production. As concrete stands as the second most extensively utilized material globally, its pervasive use amplifies the release of potent greenhouse gases. This paper introduces a novel approach to carbon capture in concrete materials by employing CO2 adsorbents that synergistically enhance the carbonization reaction, thereby augmenting capture efficiency. Biochar emerges as a promising candidate for carbon capture due to its robust CO2 adsorption capacity and its eco-friendly, cost-effective, and low-carbon production process. For instance, typically 1 ton of biochar has potential to sequester 3 ton of carbon dioxide from the environment. Various studies have explored the integration of biochar into concrete materials, aiming to improve mechanical, durability, and thermal properties, as well as the overall functionality of formed concrete composites. Beyond its role in enhancing concrete properties, biochar presents itself as an effective carbon sequestering agent with or without modification which is also reviewed in this paper. Concurrently, research efforts are underway to investigate the reinforcement properties and selective CO2 sorption capabilities of cellulose-based materials in concrete composites. Noteworthy attributes such as abundance, biodegradability, renewability, and cost-effectiveness position cellulose-based materials as promising alternatives to traditional reinforcing agents. This paper provides a comprehensive review of the latest advancements in the utilization of biochar and cellulose materials in concrete composite applications. Emphasis is placed on evaluating the durability, mechanical properties, and carbon capture potential of concrete composites augmented with biochar and cellulose. The synthesis of research progress in this domain serves to elucidate the current state of knowledge and offers insights into the future prospects of biochar and cellulose-enhanced concrete composites in the context of sustainable construction practices.

Upon the initial contact of hydrophilic cementitious materials with water, capillary absorption becomes the dominant phenomenon leading to durability deterioration of structures. The water absorption characteristics of such materials are governed by the interplay between pore structure and surface-free energies, with the latter being a factor often overlooked. In this study, advanced inverse gas chromatography (IGC) measurement techniques were employed to investigate the one-dimensional capillary water absorption of ordinary Portland cement (OPC) and alkali-activated slag (AAS). Results revealed water sorptivity values for OPC, AAS(NaOH), and AAS(Waterglass) as 0.0112, 0.0137, and 0.0187 mm/s0.5, respectively. This phenomenon can be attributed to the higher total surface-free energies observed at the liquid-solid interface in AAS materials, measuring 100.10 and 119.56 mJ/m2, compared with 74.25 mJ/m2 for OPC, consequently increasing capillary pressures. Moreover, it is observed that OPC exhibited a more complex pore tortuosity in comparison to AAS. This study underscores the dual role played by both capillary pressures and pore tortuosity in determining the water absorption characteristics of cementitious materials.

Superabsorbent polymers (SAP) are considered as a promising assortment of chemical admixtures which present novel prospects for influencing the properties of cementitious materials in the fresh, setting, and hardened states. However, the diversity of commercial SAP, especially in terms of monomers, crosslinking agents, and synthesis methods, still poses many obstacles in their large-scale application. Therefore, this review aims to shed light on intrinsic absorption and release mechanism of various SAP and its impact on rheological properties, mechanical properties, shrinkage properties, and durability for cementitious materials. Our research findings indicate significant differences in the water absorption and release mechanisms between ionic and non-ionic SAP. The swelling of non-ionic SAP is dependent on the osmotic pressure formed between the polymer network and the solution. In contrast, ionic SAP not only exhibits osmotic properties but also generates charged hydrophilic groups in solution, which is a crucial factor contributing to polymer swelling. The water absorption characteristics of SAP facilitate the regulation of early cement matrix hydration and ensure the long-term stability of the concrete structure. These attributes are crucial for maintaining stable development in cement hydration and ensuring the overall structural integrity over time. The knowledge gleaned from this review offers a robust framework for the further research work on SAP and serves as support for practical application of internally cured concrete in construction engineering that need to withstand challenging environmental conditions.

While several studies have assessed the applicability of using biochar in cement mortar and concrete preparation based on the best mechanical properties, this evaluation method should be improved to consider the techno-economic feasibility and the environmental impacts. To address this research gap, this study attempts to compare between the conventional concrete with 100 % cement as a control mixture (CM) and dumping of sludge into open sites (scenario_1), and biochar concrete using alum sludge biochar (ASB) as a partial cement replacement (scenario_2), regarding the project life cycle assessment (LCA) and economic feasibility. A multi-criteria decision-making (MCDM) framework was used to assign scores to the environmental LCA criteria, material functional performance tests, and cost considerations. The two scenarios were arranged in SimaPro LCA software, and then the different criteria were analyzed using the TOPSIS technique to choose the best alternative. The study demonstrated that the functional properties of the cement mixture containing 5 % of ASB were almost comparable to those of CM, owing to the presence of significant amounts of quartz (SiO2) that bonded strongly with cement molecules. This ASB mixture also enjoyed the least environmental impacts, reducing the global warming potential (GWP) by 32.2 % compared with the CM scenario. The scores of the “Cost” criterion, considering the price of raw materials, energy, production, and maintenance, for the two alternatives were almost comparable, depicting that scenario_2 achieved the highest closeness coefficient of 0.95 in the MCDM overall scoring. This study concluded that biochar could be incorporated into cementitious mixtures due to its lower impact on global warming to maintain a sustainable and economic concrete industrial strategy. Future studies should focus on studying the long-term durability of the biochar-based concrete mixtures and integrating into the MCDM strategy; in addition, determining the correlation between sustainable construction implementation and sustainable development goals achieved.